1. Field of the Invention
The present invention relates to a polishing apparatus and a polishing method, and more particularly to a polishing apparatus and a polishing method for polishing and flattening a polishing object, such as a semiconductor wafer, with the use of a polishing liquid (slurry).
2. Description of the Related Art
With the recent progress toward higher integration of semiconductor devices, circuit interconnects are becoming finer and the distance between adjacent interconnects is becoming smaller. Especially when forming a circuit pattern by optical lithography with a line width of not more than 0.5 μm, a stepper requires a high flatness of imaging surface because of the small depth of focus. A polishing apparatus for carrying out chemical mechanical polishing (CMP) with the use of a polishing liquid is known as such a means for flattening a surface of a semiconductor wafer.
Such a chemical mechanical polishing (CMP) apparatus includes a polishing table having, on its upper surface, a polishing pad, and a top ring. A semiconductor wafer is put between the polishing table and the top ring, and the semiconductor wafer, held by the top ring, is pressed against a polishing surface of the polishing pad while supplying an abrasive liquid (slurry) to the polishing surface, thereby polishing a surface of the semiconductor wafer into a flat mirror-like surface (see Japanese Patent Laid-Open Publication Nos. 2002-113653, H10-58309, H10-286758, 2003-133277 and 2001-237208).
The applicant has proposed a polishing apparatus and a polishing method which can achieve increased polishing rate and enhanced in-plane uniformity of polishing rate by the provision of a polishing liquid supply port for supplying a polishing liquid to a polishing surface and of a movement mechanism for moving the polishing liquid supply port so that the polishing liquid will uniformly spread over an entire surface of a polishing object due to the relative movement between the polishing object and the polishing surface (see Japanese Patent Laid-Open Publication No. 2006-147773).
The applicant has also proposed a polishing apparatus which uses a top ring having a plurality of pressure chambers for independently applying pressures on a plurality of areas of a polishing object and independently controls the pressures on the plurality of areas of the polishing object (see Japanese Patent Laid-Open Publication No. 2008-503356). A polishing apparatus is also known which uses air bags to independently control pressures on a plurality of areas of a polishing object.